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Apart from the 3 states of matter, there are 2 more states
Plasma is not a common state of matter on the earth ,
but a common one among stars which produces that
excessive heat & light.That means plasma matter has
high kinetic energies.
In contrast to this , Bohr-Einstein condensate(BEC) has
very low & even zero kinetic energies.
Due to this zero kinetic energies atoms loose their
molecular motions & begin to clump together and form
condensates named BEC’s.
We have to make a note that kinetic energies are directly
proportional to absolute temperatures & hence BEC’s
also would form & exist at extremely low temperatures.
As we all know the properties of gases or the gas
The formost property is DIFFUSION of GASES
Diffusion is the movement of gases from a region of
higher concentration to a region of lower
concentration which is exactly opposite to OSMOSIS
which is a property of liquids.
Now this diffusion of gases is measured in terms of
rates of diffusion.
Rate of Diffusion(r)
The volume of a gas that diffuses in unit time is said to
be rate of diffusion (r) of a gas .
or r1/r2 = V1/V2 * t2/t1
if the two gases have equal volumes then ,
r1/r2 = t2/t1
Similar to diffusion , EFFUSION is also a property of
Effusion is defined as the movement of gases from a
region of higher concentration to that of lower
concentration through a small pore.
The best example of effusion are like…
1) Escape of air from balloon
2) Escape of air from punctured cycle tube.
3) Gas leakages from pipes / cylinders
A very imp. arena of this chapter is on gas laws.
Here we shall deal with 5 gas laws….
1) Boyle ‘s law
2) Charles law
3) Avogadros law
4) Grahams law of Diffusion
5) Dalton’s law
Lets see one by one in detail……
PV = K
The pressure of a given mass of gas is inversly
proportional to volume at constant temperature.
A graph drawn for Boyles law is shown as
Pressure vs Volume
If a graph of boyles law is drawn between P vs 1/V ,
That is represented as
Similarly if a graph is drawn among PV vs P is given as
Charles law -1
1 states that , at constant pressure for every one degree
rise in temperature , the volume of a given mass of gas
changes by 1/273 of its volume at ‘0’ degrees
Vt= V0 1+ t/273
Charles law-1 graph
A graph plotted for statement 1 of charles law is shown
Statement - 2
It states that at constant volume , pressure of a given
mass of gas is directly proportional to temperature
At constant pressure, volume of a given mass of gas is
directly proportional to temperature .
V T or P T
The graphs drawn for charles law 1 & 2 are given as
Equal volumes of all gases contain equal number of
molecules under similar conditions of temperature
V=nK V/n = K
IDEAL GAS EQUATION
From the 3 gas laws , studied till now … ideal gas
equation can be derived as follows
PV=K ……… eq 1
P=KT ……... eq 2
V= nK ………. eq 3
From 1,2 & 3 PV=nKT
Replacing constant K, with Universal gas Constant we
Values of ‘R’
NUMERICAL VALUE UNITS
GRAHAMS LAW OF DIFFUSION
Grahams law of diffusion states that the rate of
diffusion of a gas is inversly proportional to the
squareroot of density or molecular weight.
It states that , at constant temperature the total
pressure of a gas in a gaseous mixture is the sum of
partial pressures of the gases.
At const. ‘T’ ; the partial pressure of a gas is directly
proportional to its molefraction (
Kinetic gas Equation
The kinetic gas equation is given as
Types of velocities
Gas molecules exhibit with three different kinds of
1) Average velocity ( C )
2) Most probable velocity ( C p )
3) Root meansquare velocity ( C rms )
Ratio of velocities
The ratio of C p , C & Crms can be given as
1:1.128 : 1.223
INTERMOLECULAR FORCES vs
Inter molecular forces are forces which mediate
interraction between molecules; be it forces of
attraction or forces of repulsion.
These intermolecular forces of attraction are cheifly
studied as hydrogen bonding , dipole forces of
Thermal energy is the average kinetic energy of the
molecules of a substance.
Thermal energy is a very key factor for the liquifaction
Physical state of a substance always depends on the
extent of intermolecular forces & thermal energy.
REAL GAS vs IDEAL GAS
Gases which follow ideal gas equation i.e PV=nRT
are said to be ideal gases
Gases which donot follow ideal gas equation are said be
And in general , all gases are real & no gas is ideal.
The reason behind real behaviour of gases are
1) Molecules of a gas donot exhibit any forces of
attraction among them.
2) Volume of gas occupied is negligibly small wrt space
occupied by the gas.
PV P Real gas
LIQUIFACTION OF GASES
Ideal gases cannot be liquified.it is only a real gas that
can be liquified.
Gases can be liquified on cooling below their boiling
points.But if the gas to be liquified is having a very low
boiling point , then it cannot be liquified by cooling
Hence an another technique called JOULE-THOMPSON
EFFECT is to be used.
Principle behind this technique is cooling of gases by
expansion from high pressure to low pressure.
There are 2 key points to achieve liquifaction of gases
1) Critical temperature ( Ct )
2) Critical pressure ( C p )
The highest temperature at which liquifaction of gases
occurs first is Ct & the pressure required to liquify a
gas at its critical temperature is its Cp.